Death Should Be the Penalty
Abortion is murder because it's the killing of an "innocent" life. More importantly, abortion is a violation of God's commandment "Thou shalt not kill." (Exodus 20:13, Deuteronomy 5:17, et. al.) Specifically, the grounds for this judgment comes from Exodus 21:22-25:
"If men strive and hurt a woman with child so that her fruit depart from her, and yet no mischief [injury] follow, he shall be surely punished, according as the woman's husband will lay upon him; and he shall pay as the judges determine. And if any mischief [injury] follow, then thou shalt give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burning for burning, wound for wound, stripe for stripe."
First, we see here the text gives an example of an accidental abortion, not intentional abortion. If the penalty for an accidental abortion is so severe, then it's obvious that a deliberate abortion is much more severe. It is not neccesary to ban intentional abortion, since it's already eliminated by this case law.
Second, the penalty for even an accidental abortion is death. If a man mistakenly bumps into a pregnant woman during a fight and causes her to abort her child, he must suffer the death penalty. How much more, then, shall a person suffer it who deliberately induces an abortion?
Third, even if no injury occurs to the mother or the fetus, the man in this case law is liable to a fine and, indeed, should be fined. We see here that the law clearly protects the pregnant woman and her fetus.
Fourth, since even a mother bird with eggs or her young is protected by law (Deuteronomy 22:6, 7), clearly any tampering with a birth is a grave matter--destroying life is forbidden only in the exception where it is authorized by God's law.
Therefore, abortion, being murder of a life in the womb, is to be punished by death.